Having a smartphone in America can make it a lot easier to stay in touch with friends and family who are back in the UK. It can also be useful for navigating around (e.g. finding nearby restaurants or attractions with Google Maps).

The good news is it’s now really easy to take a UK smartphone and to use it in the US. You can either roam on your UK SIM card or you can buy a US SIM card upon your arrival in the States. In this article, we’ll review and compare the best SIM cards for using your smartphone in the US. We’ll also compare the cost of using different SIM cards and will discuss network compatibility with your UK handset.

Using a UK Smartphone on US Mobile Networks

Most smartphones sold in the UK will work on AT&T and T-Mobile in the USA.

Almost all UK smartphones sold in the past decade will work in the US without any problems. Typically, you can get 3G coverage from AT&T and both 2G & 3G coverage from T-Mobile USA. On a limited selection of newer handsets, it may also be possible to get some 4G coverage from the two mobile networks.

If you’re using a fairly old handset or if your smartphone was purchased outside the UK, you should double-check to make sure your handset will work. Your phone will need to support at least one of the following frequencies for it to work in the US:

You should check your manufacturer’s spec sheet to see a list of frequencies supported by your handset.

It isn’t normally possible to use a UK smartphone on Sprint or Verizon Wireless. This is because Sprint and Verizon use a different technology for their mobile networks (CDMA/EVDO) which is incompatible with most UK smartphones.

The Two Ways Of Using Your Smartphone in the US

There are two ways to use your smartphone in the US: you can either roam on a UK-based SIM card (setting it up before you go) or you can buy a new US-based SIM card upon your arrival in the States.

Roaming on a UK-based SIM card. Through international roaming, you can continue to use a UK-based SIM card when travelling in the US. You’ll continue having a UK-based phone number and will be charged for usage through your UK network. You’ll normally be able to access coverage from both AT&T and T-Mobile USA. This is our recommended option for the majority of users. With a Pay As You Go SIM card from Three UK, you can use your smartphone in the US from just £10 for up to one month. This comes with inclusive data and inclusive calls back to the UK (including to other UK-based mobile numbers travelling abroad with you).

Buying a new US-based SIM card on arrival. If you’d like a local phone number in the US, you can buy a US SIM card upon your arrival in the States. This can either be from AT&T or T-Mobile USA. You should expect to pay at least $30 plus tax (about £21.45 plus tax of around 10%). This will give you an allowance of US minutes and also an allowance of data to use on your phone (additional charges will apply for calling back to the UK). You’ll need to buy your SIM card in person when you arrive in the US (typically, you’ll also need either a US-based credit card or cash to pay for your top-up). Typically, it will only be worth getting a local US SIM card if you regularly travel there for extended amounts of time.

Roaming On Your UK SIM Card

The simplest and easiest way to use your smartphone in the US is via international roaming on your existing UK SIM card. The prices for using your phone in the US can vary depending on your home UK mobile network:

Comparison of roaming charges when using your UK-based SIM card in the US. The costs shown are for calling the UK and sending a text message to the UK. It’s always free to receive a text message wherever you are in the world.

If you’re roaming on a UK-based SIM card, you can normally benefit from coverage on both AT&T and T-Mobile USA (your smartphone will automatically choose the network offering the strongest coverage).

The Best Network For Roaming in the US

Three is by far the cheapest mobile network for roaming in the US. When travelling to the United States of America, customers on Three can use their normal UK allowances at no extra charge. The offer is open to customers on both Pay Monthly (Advanced plans only) and Pay As You Go. For more information, please read our full review of the Feel At Home offer.

If you’re not currently a customer of Three, you can benefit from the offer by ordering a Three Pay As You Go SIM card. For instance, a £10 top-up will give you 3000 minutes, 3000 texts and 1GB of internet (up to 30 days usage in the US). You can upgrade this to 5GB of data for a £15 top-up or 12GB of data for a £20 top-up:

With an “All in One” Pay As You Go bundle, the inclusive minutes, texts and internet can be used abroad in the United States at no additional charge.

Your inclusive minutes and texts can only be used for calling a UK-based phone number. This includes any friends or family members who are also abroad with you at the same time and using a UK-based phone number (your friends or family members could also be using another SIM card from Three). Phone calls to a US-based phone number will cost you £1.40/minute extra.

As an alternative to the Feel At Home offer, customers on an EE Max tariff will also get roaming in the US included with their plan.

Buying A US SIM Card On Arrival

If you regularly travel to the United States for an extended amount of time, you might be better off buying a local SIM card from one of two US networks. If you’re using your unlocked UK smartphone, you have the option of a SIM card from either AT&T or T-Mobile USA. Unfortunately, the Sprint and Verizon networks will not work on most UK-purchased smartphones.

You can buy a US SIM card upon your arrival in the States. Unfortunately, it’s not possible to buy one online as the US mobile networks will not only ship their SIM cards to the UK. You’ll be able to buy a SIM card in retailers like 7-Eleven, CVS, Target, Walgreens and Walmart. Alternatively, you can get a SIM card from AT&T or T-Mobile retail stores.

AT&T

AT&T is the biggest mobile network in the US. They’ve been established for a longer amount of time than T-Mobile USA, which gives them better nationwide coverage. At present, AT&T claims to offer 99% population coverage on 3G and 4G (their 2G service closed down in January 2017).

On AT&T, you can get a prepaid plan from $35/month plus tax. AT&T’s prepaid plans were historically known as “GoPhone” and as such, may still be referred to by this name in some places.

For a typical smartphone user visiting the US, we’d recommend the $45 GoPhone plan (approximately £32/month plus tax). This will give you 6GB of high-speed 4G data along with unlimited calls & unlimited texts within the US. Phone calls back to the UK will cost you 49¢/minute (35p/minute) plus tax, or you can buy the $5/month International Long Distance Package which gives you 250 minutes for calling a UK landline (approximately £3.58/month plus tax).

If you’re staying in the US for an extended amount of time, you may be able to get a $5/month discount by enrolling in AT&T’s AutoPay programme. We wouldn’t recommend this if you’re a short-term visitor as it means your AT&T SIM card will be topped up automatically every month.

Finally, it’s worth being aware that your AT&T prepaid SIM card will be deactivated automatically if you don’t top it up again within 60 days of your previous bundle expiring. For this reason, it will only be possible to re-use the SIM card on a subsequent trip if you plan to visit the US again within a 60-day period.

T-Mobile

In the US, T-Mobile is the third-largest mobile network when measured in terms of number of subscribers. It is a separate and independent network from T-Mobile UK, and the two should not be confused with each other.

On T-Mobile, there are two types of prepaid package. For short one-off trips, you can choose the 21-day International Tourist Plan. Meanwhile, regular visitors and customers who want to stay for more than 21 days can choose a regular prepaid package like Simply Prepaid or T-Mobile One.

For short-term visitors, we’d currently recommend the 21-day International Tourist SIM card. This comes with 1,000 US minutes, unlimited texts and 2GB of 4G data (beyond that, you’ll still be able to use the SIM card but speeds will be restricted to 150kbps or 0.15Mbps). The International Tourist Plan costs $30 plus tax (£21.45 plus tax). It cannot be renewed at the end of the 21-day period.

If you choose a regular prepaid package, it’s possible to get a larger allowance of data. The following table shows available options from T-Mobile USA (prices and allowances are shown on a per-month basis):

If you choose the International Tourist Plan, your SIM card will expire after 21 days. Meanwhile, with other prepaid plans, you’ll be able to renew the bundle to continue using it. However, your SIM card will expire if you don’t top it up for a period of 90 days. For this reason, you’ll only be able to re-use your SIM card on subsequent trips if you expect to visit the US at least once every 3 months.

Our Recommended Deal

For the majority of visitors to the US, we’d recommend roaming on a UK-based SIM card. Three is by far the best UK mobile network from which to get a Pay As You Go SIM card. The SIM card is free and a top-up from £10 will get you up to 30 days usage over in the USA.

The following table gives a quick summary of the two options we’ve discussed in this article:

You’ll get the SIM card sent to your UK address so there’s one less thing to worry about when you arrive in the States. The SIM card will also work on both the AT&T and T-Mobile US networks. You’ll get a UK-based phone number and you’ll be able to use the inclusive minutes and texts to contact other UK-based numbers (this includes your friends and family who are also abroad with a UK-based number).

We would only recommend buying a local SIM card upon your arrival in the States if you’re a frequent traveller requiring a US-based phone number. Of the two possible networks, AT&T has slightly lower prices so is our recommended network for anyone choosing a US-based SIM card.

Other Top Tips For Travelling To The US

You’ll need to make sure your electronic devices have sufficient amounts of power before boarding the flight. Portable chargers can therefore be a great investment.

When travelling to the US, it’s also worth bearing the following things in mind:

You’ll need an ESTA to fly to the US (it costs $14 or approximately £10 per person). If you’re travelling to the US by air or by sea (even if you’re only transiting through the US to another country), you’ll need to complete an online ESTA form (from the US Electronic System for Travel Authorisation). It costs $14 per person and lasts for two years (this is approximately £10 per person). There’s more information about this on GOV.UK and Money Saving Expert. You should always apply for your ESTA on the official website run by the US Department of Homeland Security.

Make sure your electronic devices have power before boarding. As of July 2014, there are extra security measures for travellers to the US. All electronic devices being carried in your hand luggage should have sufficient amounts of power for you to be able to turn them on. This includes your smartphone, tablet, laptop and e-book reader. You could be asked to switch on the device and to demonstrate its function when passing through airport security. As there are only limited charging points available at the airport, it’s probably a good idea to invest in a portable charger (prices start from around £12).

Use TSA approved locks for securing your baggage. If you’re using a lock to secure your baggage, it must be TSA approved (see Amazon.co.uk for a list of TSA approved baggage locks). If you use a non-TSA approved lock, security teams at the airport may take a bolt cutter to your lock.

Your Comments
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We'd love to hear your thoughts and any questions you may have. So far, we've received 292 comments from readers. You can add your own comment here.

Johnsaid:

These are great ways of phoning back home. Without buying a us SIM card, I am not sure of the best option for ringing USA from within USA for booking hotels, taxi and arranging things. £1.40 pm will soon add up. Would it be possible to use data on the 3 SIM and an app like Rebtel to make internet calls within USA?

Hi John,
Thanks for your comment. You’re right: the SIM card from Three isn’t great for making phone calls directly to a US-based phone number (+1). However, like you said, you can side-step this by using a voice-over-IP app like Rebtel, Google Voice or Skype 🙂
Hope this helps,
Ken

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About Ken

My passion is helping people to get the most out of their mobile phone. I've been blogging at Ken's Tech Tips since 2005.

Aside from writing about mobile technology, I have an interest in software development, digital marketing and physics. Outside of the blog, I work with numerous technology companies helping them to market their product to consumers. Find out more.